Photo: National Institute of Allergy and Infectious Diseases
Immunotherapy has succeeded in allowing HIV patients to keep their infection under control temporarily. In addition, another patient has been completely cured of HIV by stem cell transplantation.
The seventh person ever appears to have been cured of HIV by stem cell transplantation, and triple immunotherapy enables HIV patients to go without antiretroviral therapy for months at a time. These two breakthroughs are reported by Nature on 3 December in two independent studies.
Cocktail
For the triple immunotherapy, ten HIV patients in a clinical trial first receive a DNA vaccine. This vaccine targets two components from the interior of the HIV virus. The patients are then given a cocktail of different antibodies. As a third step, they receive a further antibody injection whilst simultaneously stopping the antiretroviral medication they had previously been taking. Although the therapy fails in three of the ten patients – who experience a typical relapse in which HIV particles rapidly multiply – the remaining seven patients keep the HIV virus under some degree of control.
One of those seven patients experiences no relapse at all – at least not during the eighteen-month study period. In the other six, the number of HIV particles remains at a low level for two to six months before they too relapse and return to antiretroviral medication. A common factor among these seven patients is a marked increase in certain T cells following immunotherapy.
Although the results are mixed in terms of success, the researchers believe they are on the right track. ‘I believe we are finally making real progress in developing a therapy (…) without the need for lifelong medication’, says last author Steven Deeks in a press release.
Cure
A genuine cure does appear to be the case for a German man with HIV, who underwent a stem cell transplantation in 2015 due to acute leukaemia and has since remained HIV-free for at least three years without depending on antiretroviral medication. This procedure had previously led to a cure in six other HIV patients – or at least to a sustained reduction of HIV particles to undetectable levels. What is remarkable this time is that the donor, like the German man himself, did not carry two copies of a mutated gene for CCR5, but only one. In most other cases, the donors did carry two mutant copies. The CCR5 receptor is essential for HIV to enter a cell, so it had seemed logical that curing HIV through stem cell transplantation depended on sabotaging these receptors. This now turns out not to be the case, and is consistent with an earlier HIV patient from Switzerland who was cured, whose stem cell donor carried two normal CCR5 genes.